The modes of operation for a conventional four switch, non-inverting, DC/DC buck-boost converter typically include a buck mode, a buck/boost mode, and a boost mode. In the buck mode, the switches nearest the input end of the DC/DC converter (the buck section) are switched using a Pulse Width Modulated (PWM) signal if the input is significantly greater than the output. In the boost mode, the switches nearest the output end of the DC/DC converter (the boost section) are switched using a PWM signal if the input is significantly less than the output. In a region between the buck and boost modes, where the input is close to the output and practical min/max duty cycle limits can affect pure buck or boost performance, the switches of the buck section are switched using a first PWM signal while the switches of the boost section are switched using a second PWM signal.
Conventionally, the control circuitry that drives the buck and boost sections of the converter uses different equations to generate the duty cycles for the buck and boost sections, depending on whether the input is rising or falling past the mode transition. Disadvantages associated with conventional DC/DC converters because of this technique include control circuitry that is relatively complex and glitches that occur in the output during mode transitions. Another disadvantage is that two different efficiency curves exist for the DC/DC converter, one for when the input is falling with respect to the output, and one for when the input is rising with respect to the output. It is therefore desirable to create a new DC/DC converter.